Briton Stephen Cummings powered away on the Col d’Aspin to claim a second career Tour de France stage win as overall race contender Thibaut Pinot cracked in a seventh stage that ended in chaos on Friday.

As Team Dimension Data rider Cummings celebrated his stunning solo win, back down the road the inflatable arch marking 1km to go deflated and slowed down the bunch, even sending fellow Briton Adam Yates crashing.

Organisers said they would probably take into account the times at the 3km mark.

Cummings, who last year won in Mende, jumped away from the day’s breakaway and held off 2014 Tour champion Vincenzo Nibali on the Col d’Aspin, the first big climb this year, before descending safely to the Lac de Payolle to give his African-based team their fourth stage win this year.

Mark Cavendish had already won three sprints and Cummings showed again that Dimension Data could also play a role in the mountains as the Tour entered the Pyrenees.

“Of all my victories, I think it’s the best one. The Tour is the Tour, it’s special,” Cummings said.

“I didn’t need to win a stage this year. I had a different condition from last year as I started the Tour riding for Mark [Cavendish] who is such a winner and an inspiration.

“It’s brilliant, it’s fantastic.”

In the main bunch, Pinot’s FDJ team pulled in front at the foot of Aspin, a 12km ascent at an average gradient of 6.5 per cent, but the Frenchman, third in the 2014 Tour and one of the top favourites, was then dropped, his face a mask of pain.

He crossed the line more than two and-a-half minutes behind the other top guns.

South African Daryl Impey (Orica-Bike Exchange) was second and Spain’s Dani Navarri (Cofidis) took third place 1:05 behind Cummings.

Van Avermaet, who managed to be in the day’s break, took fifth place, over a minute ahead of the top favourites to extend his lead to 6:36 over France’s Julian Alaphilippe and 6:38 over Spain’s Alejandro Valverde.

Defending champion Chris Froome and last year’s runner-up Nairo Quintana stayed fifth and seventh respectively, both 6:42 off the pace.